The present invention relates generally electrical switches and more particularly to push button switches that include a plurality of stacked non-conductive sliders.
A push button switch is a type of electrical switch that is used to regulate the flow of current from a power source to a load through the depression of one or more buttons. Due to their relatively durable and inexpensive construction, push button switches are commonly utilized as manually operable controls for a wide variety of household electrical appliances, such as food processors, blenders, air conditioners, electric ranges and washing machines.
One type of push button switch which is known in the art includes an elongated, rectangular housing constructed of a rigid non-conductive material, switch means mounted within the housing, a plurality of externally accessible push rods extending through the housing and a plurality of stacked, non-conductive sliders movably mounted within the housing.
The switch means connects a power source to the designated load (i.e., the appliance in which the switch is installed). The switch means includes a plurality of cantilever spring blade contacts that are movable between open and closed positions, the closure of each spring blade contact serving to control a corresponding operational setting for the load (e.g., a specific motor speed).
The plurality of push rods extend vertically through the top surface of the housing in a substantially parallel relationship. Each push rod includes an enlarged, rounded first end that terminates in the housing and a second end that terminates outside of the housing, the second end being adapted to permanently receive a finger-sized actuation button.
The plurality of sliders are longitudinally arranged within a corresponding recess in the housing in a front-to-back stacked relationship. Each elongated slider is constructed of an insulating material, such as plastic, and includes flattened front and rear surfaces. The bottom edge of each slider is provided with a plurality of narrow, equidistantly spaced projections, or tines, as well as a unique arrangement of raised cam surfaces formed between selected projections, each raised cam surface being dimensioned to selectively engage and pivot a corresponding spring blade contact from its closed position to its open position. Similarly, the top edge of each slider is provided with a plurality of equidistantly spaced projections as well as a unique arrangement of inclined surfaces formed between selected projections. As will be described further below, each inclined surface is positioned and dimensioned to interact with the innermost end of a corresponding push rod which, in turn, causes the slider to displace longitudinally within the housing recess.
Accordingly, in use, the depression of an actuation button serves to vertically displace its corresponding push rod deeper into the interior cavity of the housing. Based on the configuration of the top edge of the plurality of stacked sliders, the displacement of the selected push rod causes its inner end to ultimately engage the inclined surface of one or more sliders which, in turn, causes the sliders to longitudinally travel within the recess in the housing. In this capacity, it is to be understood that the pattern of cams and inclined surfaces on the stack of sliders results in the closure of at least one spring blade contact in response to the depression of a corresponding actuation button, which is highly desirable.
Examples of pushbutton switches of the type described in detail above are disclosed in U.S. Pat. No. 6,118,085 to R. Chu, U.S. Pat. No. 5,315,076 to K. Renkes et al., U.S. Pat. No. 4,362,912 to S. Woodward, U.S. Pat. No. 3,678,288 to R. Swanke et al., and U.S. Pat. No. 2,968,704 to S. Woodward et al., all of the aforementioned patents being incorporated herein by reference.
Pushbutton switches of the type described above suffer from a notable drawback. Specifically, as noted above, the plurality of non-conductive sliders are typically arranged in a stack with the front and rear surfaces of adjacent sliders lying flush against one another. Accordingly, as a slider is displaced longitudinally within the housing, its front and rear surfaces remain in constant contact with its adjacent sliders. Due to the considerable surface area of the front and rear surfaces of each slider, considerable frictional forces are created between the moving slider and its adjacent sliders during the displacement process which, in turn, can render button depression rather difficult.
In response to the aforementioned shortcoming, it is known in the art for lubricants to be used in pushbutton switches to reduce frictional forces. However, it has been found that lubricants tend to break down over time and collect between adjacent sliders, thereby further increasing the frictional force experienced between sliders, which is highly undesirable.